This invention relates to the treatment of living tissues and/or cells by altering their interaction with the charged species in their environment. In particular, the invention relates to a controlled modification of cellular and/or tissue growth, repair and maintenance behaviour by the application of encoded electrical information. Still more particularly, this invention provides for the application, by a surgically non-invasive direct inductive coupling, of one or more electrical voltage and concomitant current signals conforming to a highly specific pattern.
Several attempts have been made in the past to elicit a response of living tissue to electrical signals.
Investigations have been conducted involving the use of direct current, alternating current, and pulsed signals of single and double polarity. Invasive treatments involving the use of implanted electrodes have been followed, as well as non-invasive techniques utilizing electrostatic and electromagnetic fields. Much of the prior work that has been done is described in Volume 238 of the Annals of the New York Academy of Sciences published Oct. 11, 1974 and entitled "Electrically Mediated Growth Mechanisms in Living Systems" (Editors A. R. Liboff and R. A. Rinaldi). See also "Augmentation of Bone Repair by Inductively Coupled Electromagnetic Fields" by C. Andrew L. Bassett, Robert J. Pawluk and Arther A. Pilla published in Volume 184, pages 575-577 of Science (May 3, 1974).
The invention herein is based upon basic cellular studies and analyses which involve a detailed consideration of the interactions of charged species, such as divalent cations and hormones at a cell's interfaces and junctions.
Basically it has been established that, by changing the electrical and/or electrochemical environment of a living cell and/or tissue, a modification, often a beneficial therapeutic effect, of the growth, repair and maintenance behavior of said tissue and/or cells can be achieved. This modification or effect is carried out by subjecting the desired area of tissues and/or cells to a specifically encoded electrical voltage and concomitant current, whereby the interactions of charged species at the cells' surfaces are modified. Such modifications engender a change in the state or function of the cell or tissue which may result in a beneficial influence on the treated site. For example, in the specific case of bone growth and repair, it is possible with one electrical code, hereinafter referred to as Mode 1, to change the interaction of the ion such as Ca.sup.2+ with a cell's membranes. Whereas, with another electrical code, hereinafter referred to as Mode 2, a modification in the same cell's protein synthesis capabilities can be affected.
For example, tissue culture experiments involving the study of embryonic chick limb rudiments show that the use of a Mode 1 code signal elicits enhanced Ca.sup.+2 release of up to 50% from the competent osteogenic cell. This effect is highly specific to the parameters of the electrical code of Mode 1. Thus this code influences one major step of ossification, i.e., the mineralization of a bone growth site. Similar tissue culture studies using Mode 2 code signals have demonstrated that this code is responsible for enhanced protein production from similar competent osteogenic cells. This latter effect is also highly specific to the parameters of the electrical code of Mode 2. In other words, this code affects certain metabolic processes for these types of cells such as those involved in calcium uptake or release from mitochondria as well as the synthesis of collagen, a basic structural protein of bone.
These studies show that the electrical codes of Mode 1 and Mode 2 elicit individual tissue and cellular responses, indicating that each code contains a highly specific informational content therein. Based upon these and other studies, it has been possible to utilize Mode 1 or Mode 2 signals or a particular combination of Mode 1 and Mode 2 signals to achieve a specific response required to enable the functional healing of a bone disorder. These electrical modes have been applied successfully to human and animal patients for non-healing fractions such as congenital pseudarthrosis and non-unions as well as fresh fractures. Successes achieved in the congenital pseudarthrosis cases are particularly noteworthy, since normally 80% of children thus afflicted require amputation, since conventional treatments such as bone grafting and internal fixation are unsuccessful.
While there have been many investigations in the past of the response of living tissues and/or cells to electrical signals, clinical results to date using prior techniques have not been uniformly successful or generally accepted within the appropriate professional community. Several reasons contribute to this state. First, it has not been realized heretofore that electrical signals of very specific informational content are required to achieve a specifically desired beneficial clinical effect on tissue and/or cells. Second, most of the prior techniques utilize implanted electrodes, which by virtue of unavoidable faradaic (electrolysis) effects are often more toxic than beneficial in the treated site. Furthermore, the cells and/or tissues are subjected to a highly uncontrolled current and/or voltage distribution, thereby comprising the ability of the cells to respond, should they do so, to the applied signal. The highly uncontrolled current and/or voltage distribution also applies in the case of capacitatively coupled signals.
In contrast, the surgically non-invasive direct inductive coupling of electrical informational content of specific electrical codes as involved in the present invention produces within living tissue and/or cells a controlled response.
In brief, the present invention involves the recognition that the growth, repair and maintenance behavior of living tissues and/or cells can be modified benefically by the application thereto of specific electrical information. This is achieved by applying pulse waveforms of voltage and concomitant current of specific time-frequency-amplitude relations to tissue and/or cells by a surgically non-invasive means through use of a varying electromagnetic field which is inductively coupled through direct induction into or upon the tissue and/or cells under treatment. The information furnished to the cells and/or tissues by these signals is designed to influence the behavior of non-excitable cells such as those involved in tissue growth, repair, and maintenance. These growth, repair and maintenance phenomena are substantially different from those involved in excitable cellular activity (e.g. nerves, muscles, etc.), particularly with respect to the type of perturbation required. Thus, the voltages and concomitant currents impressed on the cells and/or tissues are at least three orders of magnitude lower than those required to affect cellular activities such as cardiac pacing, bladder control, etc.
The invention will be more completely understood by reference to the following detailed description: